The present invention relates to an expandable seal arrangement. More particularly, the present invention relates to an expandable compression ring with molded locking members for exerting an outward, radially directed force on an inner surface of a gasket to compress the gasket into sealing engagement with a wall of an opening.
Compression rings may be used to clamp an exterior surface of a resilient gasket surrounding a pipe into sealing engagement with a wall of an opening in which the pipe is inserted. The gasket is typically constructed from an elastomeric material and, when clamped into position, provides a fluid-tight seal between the pipe and the opening. Clamping is accomplished by expanding the compression ring against an interior surface of the gasket.
Expandable compression rings may be formed from either a unitary plastic or metal, such as stainless steel. Utilization of unitary plastic rings has some drawbacks. First, a unitary construction requires that an entire plastic band be formed from a relatively expensive, high strength material. The high strength material is necessary around the areas where an expansion tool is connected to the ring during clamping of the gasket in the opening of a manhole. Pressure on the order of several hundred pounds per square inch is exerted by such an expansion tool. In addition, the locking structure of a plastic ring that secures the ring in an expanded position is subjected to large forces and thus requires a high degree of strength. Another drawback of forming expandable compression rings from plastic is that a separate mold is required for each ring that is designed to be used in conjunction with a particular range of opening diameters. These molds are expensive. The expense for such molds is particularly difficult to bear for larger sized opening diameters where market demand drops off rapidly.
Plastic expandable compression rings, however, do have advantages. One of these advantages is that plastic expandable compression rings can be integrally formed from a molding process that does not require separate forming steps, such as welding, often required when rings are made from metal. Thus, the manufacturing associated with plastic rings can be less labor intensive and less expensive than with metal rings, particularly where market demand is high. Another advantage of plastic rings is that they are not subject to corrosion. Rings made from metal can corrode due to the hostile environment in which compression rings are often used. Chemical elements such as sulfur and compounds such as sulfuric acid can, over time, corrode and degrade the structural integrity of rings made from metal.
Metal expandable compression rings, however, do have advantages. One of these advantages is that metal expandable compression rings do not require molds to be formed. Such rings can be stamped rather than formed from a mold. Certain sizes of metal rings may thus be cheaper to manufacture where market demand is lower even though manual labor may be necessary for their partial assembly. The materials costs for metal rings made from such things as stainless steel are also less expensive than unitary reinforced plastic rings. Finally, metal rings do not suffer from a buckling or creeping problem occurring in some plastic rings.
A problem that exists with the use of expandable compression rings constructed either from metal or plastic is that they are formed so as to only accommodate a particular range of opening diameters. A modular design that would allow multiple strips of various lengths to be connected together to accommodate a particular range of opening diameters would reduce the number of plastic molds and metal stamping machines that would need to be constructed. This would help reduce costs both associated with constructing such machines and providing floor space and operators for them.
An expandable compression ring that solved some or all of the above-described problems associated with the use of expandable compression rings constructed from a unitary plastic or metal would be a welcome improvement. Accordingly, the present invention provides an apparatus for outwardly radially compressing a gasket into sealing engagement with a wall of an opening. The apparatus includes a continuous strip of resiliently flexible material having first and second ends. The apparatus further includes first and second integrally molded members. Structure is provided for attaching the first and second molded members adjacent respective first and second ends of the strip. Finally, structure is provided on the first and second members for locking the strip in an expanded position. Further structure may be provided on the first and second molded members for cooperating with a force exerting structure for moving the strip into the expanded position. The cooperating structure may include a plurality of installation lugs. At least one lug may be formed on one of the molded members and a recess or recesses may be formed in the other molded member.
The peripheries of the strip and the molded members may present a substantially continuous and uninterrupted exterior circumferential surface so that the apparatus exerts a generally uniform pressure on an inner surface of the gasket. The molded members may have radii of curvature designed to accommodate a range of gasket diameters so that the molded members and strip present the substantially continuous and uninterrupted exterior circumferential surface and exert a generally uniform pressure of an inner surface of the gasket. An edge portion of the first molded member and a portion adjacent thereto may taper so as to facilitate the provision of the substantially continuous and uninterrupted circumferential surface.
The strip may be made from either plastic or stainless steel. The molded members may be made from either a reinforced plastic, such as glass-fiber-reinforced nylon 6/6, or, alternatively, a non-reinforced plastic.
When the strip is made from metal, the attaching structure may include a plurality of rivets. When the strip is made from plastic, the attaching structure may include tenons formed on the first and second ends of the plastic strip that are disposed in mortises formed in the molded members. Open mortise and tenon joints may be secured by one or more rivets, closed mortise and tenon joints may be secured with an adhesive applied between the mortise and tenon.
Structure may be formed on the first molded member for capturing the second molded member so as to secure the second molded member during expansion of the strip. The capturing structure may include a first ledge portion and a second ledge portion extending in the same general direction as the first ledge portion so that the first and second ledge portions define a cavity into which at least a portion of the second molded member is disposed.
Guide structure may be on the first and second members that limits lateral movement of the first and second members relative to one another. In one embodiment, the guide structure includes a tab on each of two opposing sides of the first member that engage opposing sides of either the strip or the second member. The guide structure of this embodiment further includes a tab on each of the opposing sides of the second member that engage the opposing sides of the first member.
The locking structure may include integrally molded, cooperating projections. The projections may be teeth-like structures on the first and second molded members that are angled in generally opposite directions.
The strip and molded ends may be expandable into multiple lock positions.
Another embodiment of the present invention includes an apparatus having a plurality of continuous strips of resilient flexible material. Each of the strips has first and second ends. The apparatus also includes structure for aligning and securing the first end of each one of the strips adjacent the second end of another of the strips so as to form a closed ring. The aligning and securing structure includes at least one set of first and second integrally molded members. Structure is provided for attaching the first and second molded members to respective ends of adjacent strips. Structure is further provided on the first and second molded members for locking the closed ring in an expanded position.
Structure may be provided on the first and second molded members for cooperating with a force exerting structure for moving the strips into the expanded position.
The strips may be made from either plastic or stainless steel. The molded members may be made from either a reinforced plastic, such as glass-fiber-reinforced nylon 6/6, or, alternatively, a non-reinforced plastic.
The molded members of the apparatus may have radii of curvature designed to accommodate a range of opening diameters so that the strips and the molded members present a substantially continuous and uninterrupted exterior circumferential surface on an inner surface of the gasket. Edge portions of the first molded member and a portion adjacent thereto may taper so as to facilitate the provision of the substantially continuous and uninterrupted circumferential surface.
When the strips are made from metal, the attaching structure may include a plurality of rivets. When the strips are made from plastic, the attaching structure may include tenons formed on the first and second ends of the strips that are disposed in mortises formed in the molded members. Open mortise and tenon joints may be secured by one or more rivets. Closed mortise and tenon joints may be secured with an adhesive applied between the mortise and tenon.
Structure may be provided on the first molded member for capturing the second molded member so as to secure the second molded member during the expansion of the strips. The capturing structure may include a first ledge portion and a second ledge portion extending in the same general direction as the first ledge portion so that the first and second ledge portions define a cavity into which at least a portion of the second molded member is disposed.
Guide structure may be on the first and second members that limits lateral movement of the first and second members relative to one another. In one embodiment, the guide structure includes a tab on each of two opposing sides of the first member that engage opposing sides of either the strip or the second member. The guide structure of this embodiment further includes a tab on each of the opposing sides of the second member that engage the opposing sides of the first member.
The locking structure may include integrally molded cooperating projections.
The first and second members may provide a range of adjustability of the circumference of the closed ring. In addition, the aligning and securing structure may include two or more sets of first and second integrally molded members that provide an additional range of adjustability of the circumference of the closed ring.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.